Geological map of the French Massif Central (modified after Chantraine et al., 2003). Metamorphic rocks comprise (i) a low-grade metasedimentary sequence attributed to the Lower Paleozoic (Cambrian to Lower Carboniferous), (ii) micaschists and paragneisses of uncertain age but considered as Neoproterozoic to Lower Paleozoic deposits, (iii) orthogneisses with a Cambrian or Ordovician age. The Middle Allochthonous Unit, the Parautochtonous Unit and the Lower Gneiss Unit are made of these metasedimentary rocks and orthogneisses. The Upper Gneiss Unit is characterized by relics of granulite facies metamorphism and by enclaves-boudins of mafic and ultramafic rocks affected by eclogite facies metamorphism, designated as the Leptynite-Amphibolite Complex (LAC). The color scheme of magmatic rocks is indicative of their age. Granitoids are distinguished according to their petrologic types in Figure 6.